The present invention relates to a support and retention device for luggage-rack bars, so-called carryall bars, adapted to allow the installation of said bars both on motor vehicles equipped with lateral driprails and on more recent motor vehicles which are not equipped therewith. For this second type of motor vehicle, it is very important that the support and retention device be capable of exerting a firm locking of the resting feet of the uprights against the roof sheet of the motor vehicle and at the same time that this device be able to ensure that the uprights are and remain correctly arranged transversely so as to correspondingly ensure the correct and constant hooking of the locking element of each upright onto the undercut profile of the bodywork with which said locking element engages.
For this purpose, devices are known in which the locking force is used both to produce and maintain the forced resting of the feet of the uprights on the roof of the motor vehicle, and to produce the transverse sliding of each pair of counterposed uprights with respect to the related bar so as to also obtain transverse locking.
These known devices, however, have not produced satisfactory results since they are unable to oppose effectively the transverse thrust which is transmitted to the uprights as an effect of the deformation of the bars produced by the load. Consequently, the loading capacity of the bars is considerably reduced, and the safety against accidental uncoupling of the supports while the vehicle is moving is not satisfactory.